The formation of eggs and sperm, which is vital to the survival of animal species is accomplished by a fundamentally similar series of processes throughout the animal kingdom. These processes depend on the ordered occurrence of a number of individual gene-controlled steps which re organized into a complex set of reactions. A major goal of this laboratory is the dissection of this network into its separate components through the study of spermatogensis and meiosis in Drosophila melanogaster. Our studies of spermatogensis are the genetic, morpholoigcal, and molecular levels, and are concerned with both the genic and chromosomal factors that are curcial to male fertility: (1) The structure and function of the Y chromosome will be investigated using segmental aneuploidy to generate duplications and deficiencies of regions that play a role in spermatogensis. Aneuploid animals will be studied at the ultrastructural level using electron microscopy. Recombinant DNA technology will be used to isolate fragments of the Y chromosome and to investigate transcripton during spermatogenesis. (2) By genetic complementation studies we will determine the degree of which lethal mutations fail to complement sterile mutations and thus estimate the level of coincidence among loci that can mutate to letahl and those that can mutate to sterile alleles. (3) We will determine the effects of duplication and deficiencies for the base of the X crhomosome on male fertility by studying the interaction of a single heterochromatic deficiency with a graded series of free - Xh duplications. Molecular probes will be used for in sity cytological characterixation of the proximal X heterochromatin of various rearranged chromosomes. A fourth project is concerned with an enzyme that cleaves N-terminally acetylated amino acids from oligopeptides and that is found at high levels in spermatids. The first of two studies of meiosis is concerned with the characterization of a number of EMS-induced female meiotic mtuations to ascertain their effects on autosomal disjunction and recombination, and on mitotic chromosome stability. The second is concerned with a Y-linked locus required for normal meiosis but not for male fertility. The meiotic behavior of males deficient for this locus are to be characterized cytologically and genetically.